This invention relates to electrical protection apparatus, and more particularly to a low cost indicator of excessive temperature at the terminals of an electrical device and temperature responsive circuit interrupter.
Most items of electrical apparatus intended for operation from commercial power sources characteristically employ terminations for the wiring that supply them with power. For proper and safe operation, these items of electrical apparatus must be wired correctly at their terminations. An improperly terminated conductor, whether the termination be the contacting blade surfaces of a plug-in type connection or a terminal connecting a stranded or solid conductor, may overheat at such termination when carrying current, bringing with it the hazard of damaging any combustible material that may happen to be in contact with the overheated terminal. If detected before an excessive temperature rise has occurred, however, this hazard can be overcome by opening the circuit which brought it about, and then removed by correcting the wiring. Therefore, it would be desirable to provide a simple, low cost temperature responsive circuit interrupter and indicator that can reliably remove electrical current from a circuit after the temperature of the electrical wiring thereof has exceeded a predetermined temperature threshold in order to avoid potential hazard due to electrical wiring overheating and to prevent continued overheating and that can signify that an excessive temperature rise has occurred.
Accordingly, one object of the invention is to provide low cost apparatus for interrupting the current flow of current-carrying electrical conductors when the temperature thereof exceeds a predetermined threshold.
Another object is to provide apparatus for reliably identifying improper termination of electrical conductors without need for any power supply other than the line voltage.
Another object is to provide apparatus which signals an indication of overheating in an electrical circuit.